package com.xneure.utils.cipher;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.SecureRandom;

/**
 * 支持SHA-1/MD5消息摘要的工具类. 返回ByteSource，可进一步被编码为Hex, Base64或UrlSafeBase64
 */
public class Digests{
	private static final String SHA1 = "SHA-1";
	private static final String MD5 = "MD5";
	private static SecureRandom random = new SecureRandom();

	/**
	 * 对输入字符串进行sha1散列.
	 */
	public static byte[] sha1(byte[] input){
		return digest(input,SHA1,null,1);
	}

	public static byte[] sha1(byte[] input,byte[] salt){
		return digest(input,SHA1,salt,1);
	}

	public static byte[] sha1(byte[] input,byte[] salt,int iterations){
		return digest(input,SHA1,salt,iterations);
	}

	/**
	 * 对字符串进行散列, 支持md5与sha1算法.
	 */
	private static byte[] digest(byte[] input,String algorithm,byte[] salt,int iterations){
		try{
			MessageDigest digest = MessageDigest.getInstance(algorithm);
			if(salt != null){
				digest.update(salt);
			}
			byte[] result = digest.digest(input);
			for(int i = 1;i < iterations;i++){
				digest.reset();
				result = digest.digest(result);
			}
			return result;
		}catch(GeneralSecurityException e){
			throw new RuntimeException(e);
		}
	}

	/**
	 * 生成随机的Byte[]作为salt.
	 *
	 * @param numBytes byte数组的大小
	 */
	public static byte[] generateSalt(int numBytes){
		byte[] bytes = new byte[numBytes];
		random.nextBytes(bytes);
		return bytes;
	}

	/**
	 * 对文件进行md5散列.
	 */
	public static String md5(InputStream input) throws IOException{
		byte[] digest = digest(input,MD5);
		return SimpleEncode.encodeHex(digest);
	}

	public static String md5(byte[] input) throws IOException{
		return md5(new ByteArrayInputStream(input));
	}

	/**
	 * 对文件进行sha1散列.
	 */
	public static byte[] sha1(InputStream input) throws IOException{
		return digest(input,SHA1);
	}

	private static byte[] digest(InputStream input,String algorithm) throws IOException{
		try{
			MessageDigest messageDigest = MessageDigest.getInstance(algorithm);
			int bufferLength = 8 * 1024;
			byte[] buffer = new byte[bufferLength];
			int read = input.read(buffer,0,bufferLength);
			while(read > -1){
				messageDigest.update(buffer,0,read);
				read = input.read(buffer,0,bufferLength);
			}
			return messageDigest.digest();
		}catch(GeneralSecurityException e){
			throw new RuntimeException(e);
		}
	}
}
